The present invention relates to a shield device for shielding electronic components on a printed circuit board, and particularly to an EMI Shield easily assembled to and disassembled from a printed circuit board of a mobile phone.
Mobile phones are subject to external EMI which can result in signal distortion. Thus, EMI sensitive electronic components on a printed circuit board of a mobile phone are conventionally protected from EMI by a shield. Referring to FIG. 3 (prior art), a conventional EMI shield in a mobile phone (not labeled) comprises a shield 51 soldered onto a printed circuit board (PCB) 52 to shield electronic components (not labeled) on the PCB 52. An upper cover 50 and a lower cover 53 are assembled together to enclose the PCB 52 and the shield 51 therein. The shield 51 is required to be fixed on the PCB 52 via a soldering process, which is not convenient. Furthermore, in order to replace or repair the electronic components, the shield must be desoldered from the PCB. This makes any repairs inconvenient and cumbersome.
U.S. Pat. No. 5,748,455 discloses one solution to the problem mentioned above. Referring to FIG. 4 (prior art), a lower cover 67 forms a plurality of posts 69 therein, each post defining a threaded hole (not labeled) therethrough for engaging with a corresponding screw 70. A PCB 61 defines a plurality of threaded holes 62 corresponding to the posts 69. A shield 63 defines a plurality of cutouts 66 at edges thereof for fitting to the periphery of the posts 69. A plurality of spring pieces 64 sidewisely extends from edges of the shield 63, and a plurality of retaining pieces 65 perpendicularly projects from edges of the shield 63 adjacent the spring pieces 64. In assembly, the spring pieces 64 abut the PCB 61, and the retaining pieces 65 abut an inner wall 68 of the lower cover 67 and the PCB 61. The screws 70 are extended through the posts 69 and threaded holes 62 of the PCB 61 and are secured in an upper cover 60. Therefore, the upper and lower covers 60, 67, the shield 63 and the PCB 61 are fixedly assembled together.
The prior art, comprising posts, threaded holes, screws, spring pieces, and retaining pieces, is unduly complicated and cumbersome. The prior art shield is designed to shield the entire PCB, whereas only certain components on the PCB need be shielded to obtain the desired protection from external EMI.
Therefore, a mobile phone with simplified shielding design is desired.
A main object of the present invention is to provide an EMI shield device for use in a mobile phone, wherein a shield is easily detached from the phone""s printed circuit board (PCB). This simplifies repair or replacement of electronic components on the PCB.
A shield device in accordance with the present invention comprises an upper and a lower covers, a shield and a fastening portion. The upper cover forms a plurality of latches along opposite sides of a lower surface thereof. The shield has a top wall and side flanges depending downwardly from edges of the top wall. A plurality of holes is defined in opposite side flanges of the shield for engaging with the latches, thereby securing the shield onto the upper cover. The upper and the lower covers are assembled together to enclose the PCB and the shield therein, the shield shielding the electronic components on the PCB.
An alternative fastening portion comprises screws and an upper cover with internal threaded posts downwardly depending from the lower face of the upper cover.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.